Magnum heads on a 74' 318 LA

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dusterman79

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Hey guys I've heard and read about putting the 302 series heads on a 318 and getting super performance when done right. I have also heard about putting Magnum heads on one and having better results with less machine work. Are any of you aware of this mod? If so, any suggestions or article or post links? I have a very strong 318 LA in my 74' Duster, but I want to do this head conversion along with a good cam set-up. Any suggestions please let me know. I'm not putting a 360 or Hemi in it. It seems that's all any one says to do. That's not my cup of tea. I want to do this on a tight budget.
 
You need to talk to RustyRatRod, he's built one...
I have the engine, but haven't gotten around to putting in my car yet.

Magnum heads oil through the pushrods, so you will need the appropriate lifters and pushrods. They also have 1.6 to 1 rocker arm ratio. I think they typically out flow all of the older heads, save for ones that have the 2.02 intake valves. Bigger intake valve than all but the earlier 340 heads (1.92" vs 1.88" for later 340 and all 360, 1.78" stock 318).Valves should be lighter, too as they run 8mm stems, .315" vs .375". Drawback... Don't have shaft mounted rockers...

There was a thread on here of the build, though I couldn't find it last time I looked. Maybe he can give you the link.

The engine he built was to be low budget, but make good power.
Basically a totally fresh, blueprinted .030" over 318 bottom end, magnum heads shaved to give a true 9.2 to 1 compression running a Lunati 60403 cam, appropriate lifters/pushrods and valve springs. Edelbrock RPM Air-Gap intake.
He ran numbers on his dyno program for 650cfm carb and 1-5/8" headers and showed something like 330HP around 6000RPM, 350Lb torque.

I just haven't had the money lately to purchase a proper torque converter so I can get this thing done...

Oh, and WHY can I not type 3 1 8 without spaces and NOT get that damn emoticon... Yes my 3 1 8's make me smile smile but WTF?
 
I have magnum heads on my 360LA, it's just a few things you should do. I tapped and plugged the oil passages in the block, used lifters that oil through the push rods (AMC type) and then measure for the correct pushrod length and use magnum style pushrods (hollow). One more thing, make sure the magnum heads you get are drilled for a LA type intake. My motor is sitting on the engine stand waiting for warmer weather, it's cold out there!
 
The 302 head is OK. It shines when you put work into it. It is pricey by compare. What needs to be done on a 302 to really see them work we'll is install the 1.88/1.60 - 360 valves and open up the port windows to match your intake.

The Magnum head conversion is a nice set up but also has it's price tag. While you can use them as is, the following mod is a good one IF you plan to run a cam with some decent lift. I forget at what lift the Magnum head can go to before issue, but if I remember correctly, it's just passed .500 lift.
So;

Have the machinist modify the head for the amount of big lift you plan on running if need be. Add matching springs to the cam at this time.

Above, it is noted that you "Make sure the head is drilled for "LA" intakes." This is not needed but a good idea for a wider verity of intakes that will cost less. I can only think of two heads out there right now that are dual drilled and they may not fit your intended purpose or budget.
The Magnum intakes are prices higher since there is less demand. Though there are basically 3 intakes for the Magnum head. They are as followed;

MoPar's dual plane - idle to 5500
Edelbrock's RPM - 1500-6500
MoPar's M1 single plane the book lists this intakes rpm incorrectly IMO since it is an upgraded copy of the Holley Strip dominator. It has a 3000 - 7000 RPM band and is a good race intake.
A note though, Hughesebgines has there FI. Version of Edelbrocks RPM Intake. While it is cast by Edelrock and made for Huges, it is an excellent intake that has the FI bosses cast in and ready to go.

But the intakes are the only pricey cave eat of this kind of build. So, IMHO, getting a head that is dual drilled for either intake is not needed.

As said above, use AMC lifters, remeasure your pushrod for the new length and order them hollow for oiling.

As far as cams go, what is the rest of your set up? Trans, gear ratio, tire size, car weight, the intended purpose of the car?

Also remember that any "LA" cam you get, divide the cams lift by 1.5, then multiply that by 1.6 Magnum rocker ratio for the new lift.
 
All good info... If you can buy the whole top end as a assembly,will save you major dinero. Pushrods/springs,will need to be replaced, the whole assembly is cheaper,than piece by piece.
 
Have 302 heads on a 318 in a 75 Scamp
Valve pockets cleaned up,188/160 valves, intake ports matched to an Edelbrock performer
KB flat tops and a Lunati Voodoo 401 cam.
Approx 10 to 1 compression 165 lbs cylinder pressure
Engine works like gangbusters even with a 2.76 rear
302,s are cheap if you can find them, Larger valves really wake them up.
 
The crosswind intake is less then an airgap but the same design and drilled for both style heads out of the box, it also has the bosses for injectors if you wanted to go that route. If just looking for simple and low cost just keep the heads stock, heck you can find low mile used ones that will be great. A mild cam, the lifters and pushrods, the crosswind and headers and you will be pretty happy with the motor. Should be as good as a stock 340.
 
Ouch!!! I forgot about that intake. Good lookin out!
 
Robbie2734 said:
I have magnum heads on my 360LA, it's just a few things you should do. I tapped and plugged the oil passages in the block, used lifters that oil through the push rods (AMC type) and then measure for the correct pushrod length and use magnum style pushrods (hollow). One more thing, make sure the magnum heads you get are drilled for a LA type intake. My motor is sitting on the engine stand waiting for warmer weather, it's cold out there!
Click to expand...
Still running that LA with magnum heads? I've had a shop build a 73 360LA with Edelbrock magnum heads, and I have all kinds of problems with the lifters. Curious about the work you had done to the block ... can you be more specific?
Thanks - tried to send a private message, mailbox was full.
 
65RoadRacer said:
Still running that LA with magnum heads? I've had a shop build a 73 360LA with Edelbrock magnum heads, and I have all kinds of problems with the lifters. Curious about the work you had done to the block ... can you be more specific?
Thanks - tried to send a private message, mailbox was full.
Click to expand...
Yes, I just had the car out today. Sorry about the mail box, my wife passed away a while ago and I haven't been on here much. Question, what was the problem you had with the lifters??? I used a roller cam from Bullet and it works fine for me. I did go to adjustable roller rockers to get the correct lash. I used a dual plane magnum I got here, the combo works good. Next step is FI!
 
Robbie2734 said:
Yes, I just had the car out today. Sorry about the mail box, my wife passed away a while ago and I haven't been on here much. Question, what was the problem you had with the lifters??? I used a roller cam from Bullet and it works fine for me. I did go to adjustable roller rockers to get the correct lash. I used a dual plane magnum I got here, the combo works good. Next step is FI!
Click to expand...
Sorry to hear about your wife....

I have a 73 LA360 with the Edelbrock heads, we did a roller cam (comp, .574 lift, hollow pushrods), SBC roller rockers (Edelbrock uses them for their heads) and I get little to no oil at the top end, and it's ridiculously noisy. Found out the builder missed a plug behind the oil filter plate, wasn't getting filtration, but still noisy... can't drive the car, concerned about wear. I have an LA Intake (Edelbrock) and my Magnum heads were drilled for the LA intake, eventually a port injection but currently FAST EZ-EFI. I had Comp Lifters (recommended by Edelbrock) then tried the Hughes Engines lifters (Morel)... but then never stay in adjustment, and ... valve covers inside are completely dry... so I don't think I'm getting oil to the top.
 
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My heads were only good for .510 lift, I think you might want to check the max lift on yours. have you bent any pushrods?? Something is way off, I get tons of oil to the top end. My cam's lift is .460 with the Chevy roller rockers and using stock Mopar roller lifters. The contact patch on the valves is dead on on the valve stems and the engine runs quiet. Are you bottoming the springs out???
 
The Edelbrock heads are good for .580 lift, and my cam is .574. We've done two sets of lifters, two set of pushrods, nothing bent or broken, but it's really noisy. I also just discovered he left the plug out behind the oil filter plate, so I was not getting filtration. Added the plug, but still nothing at the top end. I'm just going to pull the engine and take it to a different shop and basically start over... tired of messing with it, he did something wrong. Well, he did a few things wrong that I know of - now it's time to find out what else he did wrong. lol
 
I have done 2 LA to Magnum swaps and have been very happy with the results on both. 1 each 318 and 360.
Im about to do a 302 head swap onto a 318 that is older than the 302 heads.... I will see. Fresh from the machine shop, IDK if they did any porting or such, Im afraid to try as I don't want to screw up their seat work. I DO know that they came back to me with 16 new valves.
 
Well, we did a '73 360 block with magnum heads and had some problems. Three sets of lifters (yes, all had hole in top to oil through pushrod)
First set of lifters were Comp hydraulic rollers. No oil through pushrods, a couple drops, but that's it.
Second set of lifters were Hughes Engines hydraulic rollers - the ones David Hughes said would 'fix' the problem. Same results.
Third set of lifters were Comp solid rollers. Same results.
So the shop did a modification that he's done for years: he cuts a groove into the side of the lifter where the hole is from the oil band. We finally have oil through the pushrods.

Of course, the builder should have noticed that the top end was getting no oil, he screwed up so much on this build it's not even funny. Since I had no filtration at all, we pulled the engine completely apart and found that every bearing is toast after just five hours run time. Now the engine is torn completely apart and it's getting a full rebuild. Again.
 
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